Wedge mechanisms are widely used in mechanical devices. The most important applications of the wedge mechanisms are as force amplifiers Thus, the wedge mechanisms and their analogs are universally used in clamping mechanisms wherein relatively small forces applied manually or by means of relatively small and low power motors/actuators can be transformed into much larger clamping forces. The basic conventional wedge mechanism (the Prior Art) in FIG. 1 comprises base member 1, movable wedge member 2, and output member 3. These members have sliding frictional contacts along flat or curved conformal surfaces 4 between members 1 and 2 and along flat or curved conformal surfaces 5 between members 2 and 3. Usually the respective contact surfaces of members 1 and 2 and of members 2 and 3 are separated by a thinner or thicker layer of a lubricating material (e.g., oil). Output member 3 may apply the output force and/or motion to work organ 6, or may have itself the role of the work organ. If the former is true, there is contact surface 7 between output member 3 and work organ 6. The motion of output member 3 or work organ 6 is constrained/guided by guideways 8 of various embodiments. Application of input force Fi to wedge member 2 initiates movement of this wedge member along the contact surfaces 4 and 5 after the static friction force in the frictional contacts 4 and 5 are overcome. If there is no friction in contacts 4 and 5 (friction coefficient f=0), application of input force Fi results in development of output force Fo acting on output member 3,Fo=Fi/tan α,  (1)and also of reaction force N normal to contact surfaces 4 and acting on base member 1,N=Fi/tan α.  (2)Thus, for α<45°, Fo>Fi, the output force is greater than the input force. For small angles α, the effect is increasing so that Fo>>Fi. The displacement Δi of wedge member 2 is causing displacement Δo of output member 3 guided by guideways 8. If the vertical displacement of member 3 is allowed as shown in FIG. 1, thenΔo=Δi tan α.  (3)For α<45°, Δo<Δi, and for small α, Δo<<ΔI; Fi Δi=FoΔo for f=0.
When the friction coefficient f>0, the equation (1) is changing and becomes
                                          F            o                    =                                    F              i                                      tan              ⁡                              (                                  α                  +                  ρ                                )                                                    ,                            (        4        )            where ρ=tan−1 f is the friction angle. Equation (3) is not influenced by presence of friction, but if displacement Δi of moving wedge member 2 is very small and angle α is small (such combination is typical for clamping devices), the very small displacement Δo is not physically occurring and Δo is accommodated by elastic deformations in the mechanism.
Usually, for lubricated steel contact surfaces f=0.1-0.2, or ρ=5.7-11.3°. As a result, for small wedge angles α the ideal large magnitude of the mechanical advantage per (1) does not materialize, and actual mechanical advantage Fo/Fi for a given f deteriorates to a larger and larger degree the more the wedge angle α is reduced. For α=10° the mechanism with f=0 would deliver the output force Fo=Fi/tan 10°=5.7 Fi. However, for ρ=7° (f=0.12), from (4) Fo=Fi/tan 17°=3.3 Fi, 40% less than the ideal mechanical advantage 5.7. For α=5°, the ideal mechanism described by (1) would deliver the output force Fo=Fi/tan 5°=11.4 Fi, more than ten times force amplification. However, for ρ=7°, f=0.12, from (4) Fo=Fi/tan 12°=4.7 Fi, 60% less than the ideal mechanical advantage. Even worse deterioration from the ideal efficiency/mechanical advantage would develop for more realistic larger values of f. As a result, wedge angles smaller than α<˜5° are seldom used in practical designs and relatively high driving (input) forces should be used, thus increasing size and weight of the mechanisms, requiring two-stage mechanisms, etc. The noted above lack of mobility in the mechanism at small displacements due to static friction forces, leads to a need to increase stiffness of the mechanism and thus further increase its size, weight, and cost of the devices employing wedge mechanisms.
Since conventional (prior art) wedge mechanisms benefit from low friction and higher stiffness, usually their structural parts, such as members 1, 2, 3 in FIG. 1 are made from steel subjected to heat treatment for increasing hardness, the contact surfaces have to be made with high geometric accuracy and high surface finish. The contact surfaces have to be well lubricated and well protected since any scratches would result in increased friction and reduced efficiency. Since the sliding friction coefficients between conforming surfaces depend on vibratory environment, presence of vibrations can change the effective friction coefficients and the mechanical advantage of the mechanism. Consequently, the rated values of the mechanical advantage (clamping force) may change significantly depending on the vibratory environment, thus reducing consistency and reliability of these important mechanisms.
The friction coefficient in the contact areas can be reduced and its consistency can be enhanced by using rolling bodies (balls, rollers, etc.) between the contact surfaces of the constituting mechanical members. However, such designs require even better materials and heat treatment, higher accuracies, and are more bulky and more expensive. better materials and heat treatment, higher accuracies, and are more bulky and more expensive.